The short answer is yes. The full answer is more complicated.
Let's compare Jan 2009 vs Dec 2013 - a 5 year period.
Same Price / Better Product
In January 2009, you had (SD and) mostly 1.3MP cameras in the $500 to $800 range (online pricing, box with lens) but almost none had WDR or good low light performance.
Now, In December 2013, for the same price range ($500 to $800), you get 2MP, WDR and strong low light.
At the professional level, you are probably paying the same price for cameras but getting a lot better camera.
In 2009, companies like Avigilon, Dahua, Hikvision and Samsung were not major factors at all. Now, they all are. All of them offer lower prices than incumbents (like Axis, Sony and Panasonic).
In 2009 and even 2010, it was practically impossible to get any MP camera at less than $200. Now there are quite a number of options, led by new competitors and also by incumbents adding in 'value' lines that have less feature sets than there initial premium offerings.
It's hard to give a single number (prices declined by X% or Y%) as you are inherently mixing feature improvements and price declines but the shift over the last few years has been very significant as you can now expect really high quality IP cameras at under $500, that are significantly better than the $800+ models from 5 years ago.